Cross-cloud cost math: when serverless beats fixed tiers

Every API consumer asks the same question sooner or later: which gateway

tier should this run on? Most teams answer from habit. The right answer is

arithmetic.

I added a cost command to

api-onboarding-kit

because onboarding should include the answer. It reads the consumer spec,

does the multiplication across every gateway tier, and prints the options

cheapest first. The point is not that the numbers are perfect. They are

from public list pricing and they move. The point is that the method is

boring and it beats arguing from gut feeling.

The shape of the math

Every tier is one of two shapes:

Serverless: cost = requests x per-million price , no base.

Fixed: cost = flat monthly base , no per-request term.

Requests per month come straight from the spec:

monthly_requests = expected_rps x 86,400 x 30

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So a consumer at 10 rps average does about 25.9 million requests a month.

Run that through the…